Method of preserving latex and product thereof



' Patented June 27, 1944 METHOD OF PRESER-VING LATEX AND PRODUCT THEREOF WilliamD. Stewart, Akron, Ohio, assignor to T he B. F. Goodrich Company, New York, N. Y., a corporation of New York p No'Drawing. Original application December 21,

1940, Serial No.

371,203. Divided and this ap- 5 plication November 29, 1941, Serial No. 421,045

11 Claims.

This invention relates to a method of preserving latex, particularly fresh latex, and to the product .thereof.

Latex that has been freshly-collected from the V rubber .trees contains enzymes that, together with the bacteria picked up in handling the latex,

7 cause the latex to putrefy and coagulate within a relatively short time. Various methods of preserving the latex have been proposed in the past, such as the ammonia treatment now commonly used, but all these have been only generally effective and all have been more or less unsatisfactory. 1

I have discovered a method of preserving latex, particularly freshly-collected latex, that produces a sterile, stable latex that will stand for long periods without putrefaction or coagulation. By the method of this invention the pH of the fresh latex is adjusted to a point not less than 9.8 nor more than 10.0 by means of buffer solutions, alkalies, or the like. The preferred manner is by adding ammonia to the latex in from 0.25% to 0.35% by weight of the latex. To this latex is then added small proportions of one or more of the amino derivatives of aromatic compounds. Examples of these compounds are p-amino phenol, amino-benzoic acid, 2-amino-8-naphthol-fi-sulfonic acid, and 1-amino-8-naphthol- 3,6-disulfonic acid or, as it is commonly called, amino-H-acid. All the compounds contemplated in the present invention are at least slightly soluble in alkaline latex and generally are freely soluble therein. The compounds are preferably used in amounts ranging from not less than 0.05% to not more than 0.20% by weight of the latex although greater or smaller amounts may be used if desired. Those compounds that are acid should be neutralized with an alkali before being added to the latex. The compounds may be added either before or after the pH of the latex has been adjusted to the specified range of 9.8 to 10.0 and if necessary the pH may be readjusted after addition of the compound. The latex should be treated by the method of the invention without any undue interval of time after it has been collected from the trees, preferably within eighteen hours after such collecting.

As an example of this invention ammonia is added to fresh latex until the pH is raised to 9.9 and immediately thereafter 0.15% of p-amino phenol by weight of latex is added to the latex. This results in a well-preserved latex that will remain sweet and uncoagulated for long periods of time and that will require no blowing off of ammonia at the factory.

'As 'will be apparent from the foregoing the preserved latex prepared according to this invention ordinarily will contain only the natural latex itself and the ammonia or other material added in adjusting the pH together with the amino derivatives of aromatic compounds as described. Any of the usual compounding or conditioning agents may later be added as desired to prepare the latex for specific uses but such materials preferably are not added at the plantation.

The method of this invention produces a latex that will remain well-preserved over long periods of time with no danger of putrefaction and c0- agulation and although the method is more useful for preserving freshly-collected latex it is also applicable for and produces excellent results with latex that has been previously preserved by other methods.

This application is a division of my copending application, Serial No. 371,203, filed December 21, 1940.

Having, disclosed my invention it is my desire to protect it broadly within the spirit and scope of the appended claims.

I claim:

1. The method of preserving latex which comprises adjusting the pH of the latex to not less than 9.8 nor more than 10.0 and adding a small proportion of a member of the class consisting of p-amino phenol, amino-benzoic acid, 2-amino- 8-naphthol-6-sulfonic acid, and 1-amino-8- naphthol-3,6-disulfonic acid.

2. The method of preserving freshly-collected latex which comprises adjusting the pH of the latex to not less than 9.8 nor more than 10.0 and adding a small proportion of a member of the class consisting of p-amino phenol, aminobenzoic acid, 2-amino-8-naphthol-6-sulfonic acid, and 1-amino-8-naphthol-3,6-disulfonic acid.

3. The method of preserving freshly-collected latex which comprises treating the latex with sufficient alkali to raise the pH to not less than 9.8 nor more than 10.0 and adding a small proportion of a member of the class consisting of p-amino phenol, amino-benzoic acid, 2-amino- 8-naphthol-6-sulfonic acid, and 1-amino-8- naphthol-3,6-disulfonic acid.

4. The method of preserving freshly-collected latex which comprises treating the latex with sufficient ammonia to raise the pH to not less than 9.8 nor more than 10.0 and adding a small proportion of a member of the class consisting of p-amino phenol, amino-benzoic acid, 2-amino- 8-naphthol-6-sulfonic acid, and 1-amino-8- naphtho1-3,6-d1sulfonic acid.

6. The method of preserving freshly-collected latex which comprises treating the latex with, suflicient alkali to raise the pH to not less than" 9.8 nor more than 10.0 and adding not less than 0.05% latex of a member of 8-naphthol-6-sulfonic acid, i and l-amino-8-,,, acid, 2-amino:8-naphthol-6-sulfonic acid, and

naphthol-3,6-disulfonic acid. a

7. The method of preserving freshly-collected 8. Preserved latex having a pH not less than 9.8 nor more than 10.0 and containing a small proportion of a member of the class consisting of p-amino phenol, amino-benzoic acid, 2-amino- 8-naphthol-6-sulfonic acid, and Lamina-8- naphthol-3,6-disulfonic acid.

9.'Preserved latex having a pH not less than 9.8 nor more than 10.0 and containing an alkali and a small proportion of a member of the class consisting of p-amino phenol, amino-benzoic acid,. ,2-amino-8-naphthol-6-sulfonic acid, and

' "1 amino-8-naphthol-3,6-disulf0nic acid.

nor more than 0.20% by weight of the the class consisting citp-amino phenol, amino-benzoic acid, 2-amino-" .10. Preserved latex having a pH not less than -;9.8 nor"morethan 10.0 and containing ammonia and asmall proportion of a member of the class consisting .of p-amino phenol, amino-benzoic 1 1-amino-8- naphthol-3,6-dlsulfonic acid.

latex which comprises treating the latex with suflicient anmionia to raise the pH to not less than 9.8 nor more than 10.0 and adding not less than 0.05% nor more than 0.20% by weight of the latex of a member of the class consisting of p-amino phenol, amino-benzoic acid, 2-amino- 8-naphtho1-6-sulfonic acid, and 1-amino-8- naphthol-3,6-disulfonic acid. l

ll, Preserved latex having a pH not less than 9.8 nor more than 10.0 and containing ammonia and not less than 0.05% nor more than 0.20% by weight of the latex of a member of the class consisting of p-amino phenol, amino-benzoic acid, 2-amino-8-naphthol-6-sulfonic acid, and

1-amino-8-naphtho1-3,6-disulfonic acid.

WILLIAM D. STEWART. 

